Buggy code:
class XTSSubsystemAdd extends AbstractBoottimeAddStepHandler { static final XTSSubsystemAdd INSTANCE = new XTSSubsystemAdd ( ) ; private static final String [ ] WAR_DEPLOYMENT_NAMES = new String [ ] { "ws-c11.war" , "ws-t11-coordinator.war" , "ws-t11-participant.war" , "ws-t11-client.war" } ; private static class EndpointInfo { String SEIClassname ; String URLPattern ; EndpointInfo ( String seiClassname , String urlPattern ) { } } static class ContextInfo { String contextPath ; XTSSubsystemAdd . EndpointInfo [ ] endpointInfo ; ContextInfo ( String contextPath , XTSSubsystemAdd . EndpointInfo [ ] endpointInfo ) { } } private static final XTSSubsystemAdd . ContextInfo [ ] contextDefinitions = new XTSSubsystemAdd . ContextInfo [ ] { new XTSSubsystemAdd . ContextInfo ( "ws-c11" , new XTSSubsystemAdd . EndpointInfo [ ] { new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wscoor.sei.ActivationPortTypeImpl" , "ActivationService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wscoor.sei.RegistrationPortTypeImpl" , "RegistrationService" ) } ) , new XTSSubsystemAdd . ContextInfo ( "ws-t11-coordinator" , new XTSSubsystemAdd . EndpointInfo [ ] { new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsat.sei.CoordinatorPortTypeImpl" , "CoordinatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsat.sei.CompletionCoordinatorPortTypeImpl" , "CompletionCoordinatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsat.sei.CompletionCoordinatorRPCPortTypeImpl" , "CompletionCoordinatorRPCService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsba.sei.BusinessAgreementWithCoordinatorCompletionCoordinatorPortTypeImpl" , "BusinessAgreementWithCoordinatorCompletionCoordinatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsba.sei.BusinessAgreementWithParticipantCompletionCoordinatorPortTypeImpl" , "BusinessAgreementWithParticipantCompletionCoordinatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsarjtx.sei.TerminationCoordinatorPortTypeImpl" , "TerminationCoordinatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsarjtx.sei.TerminationCoordinatorRPCPortTypeImpl" , "TerminationCoordinatorRPCService" ) } ) , new XTSSubsystemAdd . ContextInfo ( "ws-t11-participant" , new XTSSubsystemAdd . EndpointInfo [ ] { new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsat.sei.ParticipantPortTypeImpl" , "ParticipantService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsba.sei.BusinessAgreementWithCoordinatorCompletionParticipantPortTypeImpl" , "BusinessAgreementWithCoordinatorCompletionParticipantService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsba.sei.BusinessAgreementWithParticipantCompletionParticipantPortTypeImpl" , "BusinessAgreementWithParticipantCompletionParticipantService" ) } ) , new XTSSubsystemAdd . ContextInfo ( "ws-t11-client" , new XTSSubsystemAdd . EndpointInfo [ ] { new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsat.sei.CompletionInitiatorPortTypeImpl" , "CompletionInitiatorService" ) , new XTSSubsystemAdd . EndpointInfo ( "com.arjuna.webservices11.wsarjtx.sei.TerminationParticipantPortTypeImpl" , "TerminationParticipantService" ) } ) } ; private static final String ENDPOINT_SERVICE_HOST_NAME = "default-host" ; private XTSSubsystemAdd ( ) { } static XTSSubsystemAdd . ContextInfo [ ] getContextDefinitions ( ) { } @ Override protected void populateModel ( ModelNode operation , ModelNode model ) throws OperationFailedException { } @ Override protected void performBoottime ( OperationContext context , ModelNode operation , ModelNode model , ServiceVerificationHandler verificationHandler , List < ServiceController < ? > > newControllers ) throws OperationFailedException { <START_BUG> final String coordinatorURL = ( model . get ( XTS_ENVIRONMENT ) . hasDefined ( URL ) ) ? model . get ( XTS_ENVIRONMENT , URL ) . asString ( ) : null ; <END_BUG> if ( ( coordinatorURL != null ) && ( ROOT_LOGGER . isDebugEnabled ( ) ) ) { ROOT_LOGGER . debugf ( "nodeIdentifier=%s\n" , coordinatorURL ) ; } final ServiceTarget target = context . getServiceTarget ( ) ; final ClassLoader loader = XTSService . class . getClassLoader ( ) ; ServiceBuilder < Context > endpointBuilder ; ArrayList < ServiceController < Context > > controllers = new ArrayList < ServiceController < Context > > ( ) ; for ( XTSSubsystemAdd . ContextInfo contextInfo : XTSSubsystemAdd . contextDefinitions ) { String contextName = contextInfo . contextPath ; Map < String , String > map = new HashMap < String , String > ( ) ; for ( XTSSubsystemAdd . EndpointInfo endpointInfo : contextInfo . endpointInfo ) { map . put ( endpointInfo . URLPattern , endpointInfo . SEIClassname ) ; } endpointBuilder = EndpointPublishService . createServiceBuilder ( target , contextName , loader , XTSSubsystemAdd . ENDPOINT_SERVICE_HOST_NAME , map ) ; controllers . add ( endpointBuilder . setInitialMode ( ACTIVE ) . install ( ) ) ; } final XTSManagerService xtsService = new XTSManagerService ( coordinatorURL ) ; ServiceBuilder < ? > xtsServiceBuilder = target . addService ( JBOSS_XTS_MAIN , xtsService ) ; xtsServiceBuilder . addDependency ( JBOSS_TXN_ARJUNA_TRANSACTION_MANAGER ) ; xtsServiceBuilder . addDependency ( CONFIG_SERVICE , ServerConfig . class , xtsService . getWSServerConfig ( ) ) ; for ( ServiceController < Context > controller : controllers ) { xtsServiceBuilder . addDependency ( controller . getName ( ) ) ; } xtsServiceBuilder . setInitialMode ( ACTIVE ) . install ( ) ; final TxBridgeInboundRecoveryService txBridgeInboundRecoveryService = new TxBridgeInboundRecoveryService ( ) ; ServiceBuilder < ? > txBridgeInboundRecoveryServiceBuilder = target . addService ( JBOSS_XTS_TXBRIDGE_INBOUND_RECOVERY , txBridgeInboundRecoveryService ) ; txBridgeInboundRecoveryServiceBuilder . addDependency ( JBOSS_XTS_MAIN ) ; txBridgeInboundRecoveryServiceBuilder . setInitialMode ( ACTIVE ) . install ( ) ; final TxBridgeOutboundRecoveryService txBridgeOutboundRecoveryService = new TxBridgeOutboundRecoveryService ( ) ; ServiceBuilder < ? > txBridgeOutboundRecoveryServiceBuilder = target . addService ( JBOSS_XTS_TXBRIDGE_OUTBOUND_RECOVERY , txBridgeOutboundRecoveryService ) ; txBridgeOutboundRecoveryServiceBuilder . addDependency ( JBOSS_XTS_MAIN ) ; txBridgeOutboundRecoveryServiceBuilder . setInitialMode ( ACTIVE ) . install ( ) ; } }

Fix:
final String coordinatorURL = ( model . get ( XTS_ENVIRONMENT , URL ) . isDefined ( ) ) ? context . resolveExpressions ( model . get ( XTS_ENVIRONMENT , URL ) ) . asString ( ) : null ;